Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$90.41	5.466%	$95.3518	$95.35	$95.35	$95.40
Purchase #2	$30.28	10.737%	$33.5312	$33.53	$33.55	$33.50
Purchase #3	$200.44	10.851%	$222.1897	$222.19	$222.20	$222.20
Purchase #4	$238.79	8.638%	$259.4167	$259.42	$259.40	$259.40
Purchase #5	$225.43	6.742%	$240.6285	$240.63	$240.65	$240.60
Purchase #6	$192.70	10.599%	$213.1243	$213.12	$213.10	$213.10
Purchase #7	$12.89	5.602%	$13.6121	$13.61	$13.60	$13.60
7 purchase totals =	$990.94		$1,077.8543	$1,077.85	$1,077.85	$1,077.80